Hot caustic treatment of earth formations



XR 3129760 5R 3,129,760 HOT CAUSTIC TREATMENT OF EARTH FORMATIONS Marvin Gambill, 1300 Lano Drive, Hobbs, N. Mex. No Drawing. Filed Dec. 30, 1957, Ser. No. 705,795 7 Claims. (Cl. 166-38) This invention relates to a method and composition for treatment of earth formations around oil wells to assist in improving the flow of oil coming from the formation.

It is a characteristic of an oil well that the rate of flow diminishes with time and, unfortunately, altogether too frequently the economic point at which pumping of the well should be stopped as unprofitable is reached while there still remains a very substantial quantity of oil in the formation. Reasons for the loss of flow are varied and complex but are related generally to the chemical nature of the formation, porosity, and the accumulation of wax or asphaltic deposits in the pores of the formation, as well as the accumulation of scale and other corruption in the tubes in the bottom of the well.

Acidizing techniques for relieving these congested conditions in oil wells have been developed to a highly scien tific level, in general identifiable as the matching of the reactive capacity of an acid under high pressure high temperature conditions for the chemical compounds making up the oil formation. The use of caustic alkalis in the treatment of oil formations has also been developed to a certain extent, but inasmuch as relatively few conditions yield to caustic disintegration, the technique is not common.

It is a fundamental object of this invention to provide a modified hot caustic treatment for earth formations surrounding an oil well in which the chemical and physical properties of the caustic solution are used to maximum advantages in the downhole location.

Another object of the invention is to provide a technique by which mechanical pressure and blasting at the underground levels can be accomplished.

Another object of the invention is to provide a fluid medium suitable for use in fracture treatments, either by pressure alone or by heat, pressure and even explosive treatment at the underground level.

Other objects and advantages of the invention will in part be obvious and in part appear hereinafter.

The invention, accordingly, is embodied in a process for the hot caustic treatment of an oil well and the earth formation surrounding the well in which, first, a finely divided metal such as aluminum in an oil suspension or in water is injected into the oil well under pressure, which pressure may be of fracturing levels, and is followed by a solution of caustic alkali, which may beat any temperature from ambient to boiling at the surface. With contact between the caustic and the aluminum in the underground formation, a highly exothermic reaction occurs in which hydrogen is generated together with much heat so that the formation and the solution are heated, and mechanical and chemical effects are obtained simultaneously in the earth formation. The result is a large buildup of hydrogen pressure and steam pressure in the earth formation, which produces fracturing and mechanical loosening of extraneous deposits, reducing the porosity of formation. T improve the effectiveness of the mechanical effect, an optional additional step of the operation involves, after a period of time, the introduction of an oxidizing agent,

such as sodium or potassium chlorate into the caustic solution, for example, into the last 20 or 30 percent of the caustic solution, with the result that when the oxidizing agent reaches the earth formation, hydrogen is explosively burned and actual combustion of organic compositions occurs. In general, this latter procedure is not necessary and in view of the hazards involved, it is not desirable,

3,129,760 Patented Apr. 21, 1964 except as a last final drastic measure in an effort to open the well.

In my co-pending application, Serial No. 663,915, now Patent No. 3,000,442, I describe a fracture treatment for earth formations in which sodium chloride pellets are injected under pressure in preferred medium into the earth formation. In accordance with this invention, the aqueous medium or liquid medium used in my co-pending applicationnamely, the brine or the oil may serve as the vehicle for bringing aluminum powder or pellets down into the earth formation, where it is subjected to heavy pressure for such mechanical fracture as fast as can be induced by that technique. It is to be understood that the technique described in my said application is useful in conjunction with the process described herein.

In any fracture treatment, ingredients are forced into the formation under high pressure, the pressure is main tained and when a sudden pressure drop occurs it is taken as an indication of fracture in the formation.

In the preferred practice of my invention, therefore, following the introduction of an appropriate quantity of aluminum, I add aqueous sodium hydroxide solution which need be only at ambient temperature, but may be at any temperature up to boiling. The preferred concentration of the sodium hydroxide solution is about 2030 percent solids for in this range an adequate quantity of the chemical can be introduced to the earth formation in a reasonable volume of the liquid. Typical quantities for using in the treatment of an oil well are the following:

Since the reaction of aluminum with caustic alkali is on a mole-per-mole basis, quantities may be calculated accordingly. Generally it is preferable to operate with an excess of alkali.

Following the introduction of the sodium hydroxide a very intense chemical reaction is induced in the exact areas to which the aluminum pellets penetrate, and the generation of heat at the actual site of the reaction, to gether with the generation of steam and hydrogen, induces additional fracturing and loosening of the formation.

The presence of hydrogen in the formation creates a certain explosive hazard at the well head, and the hazard can be converted to the advantage of the operator in the treatment of the earth formation,,as noted above. That is, the sodium hydroxide can be added in portions and by introducing regulated amounts of potassium chlorate, for example, by introducing an occasional few gallons of concentrated solution in the stream of the sodium hydroxide being pumped into the well, the potassium chlorate reaches the earth formation virtually intact and upon contacting the earth formation the combustible organic matter, including the hydrogen, is burned by the potassium (or sodium) chlorate with explosive violence, thus inducing further additional mechanical fracturing of the formation.

Where it is desired to use the chlorate treatment to induce additional fracturing, it is best carried out after about /z% of the caustic alkali has been added.

A real advantage of this treatment of the oil wells resides in the fact that caustic solutions, although not pleasant to handle by operators, are relatively non-corrosive in their contact with the metal parts around oil wells,

so that little attention need be paid to the prevention of corrosion. This is in direct contrast to oil well acidizing techniques where a major problem and major limitation on the use of an acid is the reduction of the extent to which it will dissolve the metal parts in the Well and associated pumps.

The chemicals useful in the operation may be any technical or commercial grades. The sodium hydroxide may be purchased as a solution in about the concentration desired.

The aluminum may be used as a powder of the finely divided type used in paints or as a chemical reagent. However, this may be economically impracticable on a very large scale. Actually the preferred form of aluminum is a relatively crude mixture of pellets, cuttings, powder, etc.

to obtain a rather random distribution of particle size to give recognition to the fact that the earth formation fissures etc., will be penetrated by such variety of sizes. Mixtures with particles of aluminum as large as /2 inch in diameter may be used. The source, as noted, may be from chemical reagent pellets, powders, foil cuttings to the much less exotic machine shop shavings or macerated pots and pans.

Though the invention has been described in relation to a single embodiment, it is to be understood that variations thereof may be practiced Without departing from its spirit or scope.

What is claimed is:

1. The method of treating earth formations to induce fractures therein to promote flow of oil which comprises, injecting into such formations under high pressure sufficient to induce fracture of said formation a liquid characterized by its carrying solid aluminum particles suspended therein, maintaining said pressure for a predetermined interval of time, to cause aluminum particles to enter said formation, introducing thereafter an aqueous caustic alkali solution under high pressure to contact said aluminum particles, thereby to induce an exothermic gas generating reaction in said earth formation, and, thereafter, releasing said pressure.

2. The method in accordance with claim 1 in which the liquid medium carrying the aluminum particles is a hydrocarbon.

3. The method in accordance with claim 1 in which the liquid medium carrying the aluminum particles is water.

4. The method in accordance with claim 1 in which the aluminum is followed by the addition of at least the stoichiometric amount of caustic alkali needed to dissolve it.

5. The method of fracture treating earth formations which comprises injecting into such formations under high pressure sufiicient to induce fracture of said formation a liquid containing about 5-25 percent by weight of finely divided metallic aluminum particles suspended therein, said aluminum at coarsest being about inch diameter particles, maintaining said pressure for a predetermined interval of time, injecting under pressure after said aluminum at least sufficient aqueous caustic alkali solutions in 550 percent concentration to dissolve all of said aluminum, forming a gas generating system maintaining said system in a closed formation until a sudden drop in pressure from the maximum pressure generated is experienced and then releasing pressure.

6. The method in accordance with claim 5 in which the liquid medium carrying the aluminum is oil.

7. The method in accordance with claim 5 in which the liquid medium carrying the aluminum is water.

References Cited in the file of this patent UNITED STATES PATENTS Barrett July 5, 1960 

1. THE METHOD OF TREATING EARTH FORMATION TO INDUCE FRACTURES THEREIN TO PROMOTE FLOW OF OIL WHICH COMPPRISES, INJECTING INTO SUCH FORMATIONS UNDER HIGH PRESSURE SUFFICIENT TO INDUCE FRACTURE OF SAID FORMATION A LIQUID CHARACTERIZED BY ITS CARRYING SOLID ALUMINUM PARTICLES SUSPENDED THEREIN, MAINTAINING SAID PRESSURE FOR A PREDETERMINED INTERVAL OF TIME, TO CAUSE ALUMINUM PARTICLES TO ENTER SAID FORMATION, INTRODUCING THEREAFTER AN AQUEOUS CAUSTIC ALKALI SOLUTION UNDER HIGH PRESSURE TO CONTACT SAID ALUMINUM PARTICLES, THEREBY TO INDUCE AN EXOTHERMIC GAS GENERATING REACTION IN SAID EARTH FORMATION, AND, THEREAFTER, RELEASING SAID PRESSURE. 